1. Field of the Invention
The present invention relates to a drive unit. More specifically, it relates to a drive unit provided in an omnidirectional vehicle.
Priority is claimed on Japanese Patent Application No. 2009-218172 filed Sep. 18, 2009, the content of which is incorporated herein by reference.
2. Description of Related Art
An omnidirectional vehicle that can move omnidirectionally on a floor surface (i.e. in all directions within two dimensions) was proposed by the present applicants in, for example, International Publication No. 2008/132778 and International Publication No. 2008/132779. In the omnidirectional vehicles in International Publication Nos. 2008/132778 and 2008/132779, a ball-shaped, or wheel-shaped, or crawler-shaped main wheel that can move omnidirectionally on the floor surface while contacting the floor surface, and an actuator that includes an electric motor for driving the main wheel, and the like, are fitted to the base of a vehicle. The actuator drives the main wheel, whereby the vehicle moves on the floor surface.
The present applicants proposed a technology for controlling this type of operation for moving an omnidirectional vehicle in JPA No. 3070015. In this technology, the base of the vehicle can tilt to the front, rear, left, and right with respect to the main wheel. The tilt angle of the base is measured, and the torque of the electric motor that drives the main wheel is controlled such as to maintain the tilt angle at a required angle, thereby moving the vehicle in accordance with the tilting operation of the base.
FIG. 9 of International Publication No. 2008/132779 discloses a wheel having an annular shaft and a plurality of sleeves (hereinafter driven rollers) which are installed on the annular shaft in such a manner that they can rotate around the axis in the tangential direction of the annular shaft and make contact with an object for generating a driving force.
The main wheel configured in this manner rotates around the center axis of the annular shaft to move forward and backwards, and the driven rollers that are making contact with the ground rotate around the tangential direction of the annular shaft to move left and right.
When the main wheel described above moves forward and backwards, edges of the driven roller makes contact with the ground contact surface to obtain a gripping force of the main wheel. However, there is a possibility that the gripping force will decrease when the drive rollers revolve and the main wheel attempt to move in the lateral direction.